NOTE FOR DATA ON THIS PAGE: Road condition is based on measured pavement roughness using the International Roughness Index (IRI). IRI is a measure of surface condition. A comprehensive measure of pavement condition would require data on other pavement distresses such as rutting, cracking, and faulting.

SOURCE FOR DATA ON THIS PAGE: U.S. Department of Transportation, Federal Highway Administration, Highway Statistics, Washington, DC: annual editions, tables HM-63 and HM-64, available at http://www.fhwa.dot.gov/ as of Feb. 1, 2002.